Evaluation of the Aptima HIV-1 Quant Dx assay for HIV diagnosis at birth in South Africa.

The increased coverage of antiretroviral therapy has resulted in a decrease in the positive predictive value (PPV) and diagnostic sensitivity of early infant diagnosis assays. To evaluate the diagnostic performance of the Aptima HIV-1 Quant DX assay (Aptima) in detecting HIV infection at birth. The study was a cross-sectional laboratory based evaluation using whole blood DBS specimens. Samples were collected from HIV-exposed neonates at birth at two paediatric facilities in Gauteng between 1st March 2018 - 31st January 2020. Performance of the Aptima compared to the Cobas® AmpliPrep/Cobas® TaqMan HIV-1 Qualitative Test v2.0 was calculated using a two-by-two table and reported as proportions with 95% confidence intervals. A total of 363 infants met the inclusion criteria of which 4 (1.1%) had an Aptima result discordant with CAP/CTM HIV status: two (50%) negative and two (50%) positive. The Aptima assay had a sensitivity of 93.75% (95% CI: 79.19%-99.23%), specificity of 99.4% (95% CI: 97.83%-99.93%), PPV of 93.75% (95% CI: 78.98%-98.36%), negative predictive value of 99.4% (95% CI: 97.73%-99.84%), and overall accuracy of 98.9% (95% CI: 97.2%-99.7%). The Aptima yielded an error code on 37 (10.19%) results, of which 35 (94.59%) were resolved on repeat testing. Of the 32 HIV-detected specimens, 20 had a plasma VL result available (18 on Abbott and 2 on Cobas). The absolute median difference was 0.66 log10 (IQR: 0.36-1.71). The Aptima demonstrated good EID performance and can be considered as a qualitative EID assay.

Point-of-care HIV maternal viral load and early infant diagnosis testing around time of delivery at tertiary obstetric units in South Africa: a prospective study of coverage, results return and turn-around times.

INTRODUCTION: Maternal viral load monitoring (mVL) and early infant diagnosis (EID) are necessary to achieve elimination of mother-to-child transmission of HIV. Point-of-care testing can achieve better outcomes compared to centralized laboratory testing (CLT). We describe the first implementation of point-of-care (POC) mVL and EID testing around delivery at four high volume tertiary obstetric units (TOUs) in Gauteng, South Africa. METHODS: Prospective study of pregnant women living with HIV (WLHIV) and their infants. During the period 1 June 2018 to 31 March 2019, routine staff collected blood specimens from women and their infants around delivery. Specimen collection occurred throughout the week while dedicated POC operators, conducted testing during working hours on weekdays. Descriptive statistics and multivariable Poisson regression with robust error variance were used to describe outcomes and associated factors. Outcomes determined were (i) coverage of mVL and EID testing defined as a proportion of live births to WLHIV admitted at each facility (ii) results returned prior to discharge (iii) turn-around time (TAT) and iv) performance of POC testing compared to CLT. RESULTS: In total, 8147 live births to pregnant WLHIV were recorded in the implementation period. Of these, 2912 mVL and 5074 EID specimens were included in the analysis, with 131 (4.5%) mVL and 715 (14.1%) EID specimens having initial invalid/error results. Overall coverage of POC mVL and EID testing was 35.6% (range 20.9% to 60.1%) and 61.9% (range 47.0% to 88.0%) respectively. Proportions of POC tested mothers and infants with results returned prior to discharge were 74.3% (range 39.0% to 95.7%) and 73.0% (range 50.0 to 97.9%). Return of results was independently associated with TOU, after-hours specimen collection, having an initial invalid or error result and period of implementation. Overall TAT for specimens collected from mother-infant pairs where both had POC testing, during weekdays was longer for EID compared to mVL testing (median 3.3 hours vs. 2.9 hours, p-value sign test <0.001). POC results were comparable to those from laboratory testing. CONCLUSION: Accurate and timely POC mVL and EID testing around delivery was implemented with variable success across TOUs. Further scale up would need to address health system factors at facility level and high analytical error rates.